﻿// Copyright 2004-2011 Castle Project - http://www.castleproject.org/
// 
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// 
//     http://www.apache.org/licenses/LICENSE-2.0
// 
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#region 导入名称空间

using System;
using System.Reflection;
using LightWork.DynamicProxy.Generators;
using LightWork.DynamicProxy.Generators.Emitters;
using LightWork.DynamicProxy.Generators.Emitters.SimpleAST;
using LightWork.DynamicProxy.Internal;

#endregion

namespace LightWork.DynamicProxy.Contributors
{
    public class DelegateTypeGenerator : IGenerator<AbstractTypeEmitter>
    {
        private const TypeAttributes DelegateFlags = TypeAttributes.Class |
                                                     TypeAttributes.Public |
                                                     TypeAttributes.Sealed |
                                                     TypeAttributes.AnsiClass |
                                                     TypeAttributes.AutoClass;

        private readonly MetaMethod method;
        private readonly Type targetType;

        public DelegateTypeGenerator(MetaMethod method, Type targetType)
        {
            this.method = method;
            this.targetType = targetType;
        }

        public AbstractTypeEmitter Generate(ClassEmitter @class, ProxyGenerationOptions options,
            INamingScope namingScope)
        {
            var emitter = GetEmitter(@class, namingScope);
            BuildConstructor(emitter);
            BuildInvokeMethod(emitter);
            return emitter;
        }

        private void BuildConstructor(AbstractTypeEmitter emitter)
        {
            var constructor = emitter.CreateConstructor(new ArgumentReference(typeof(object)),
                new ArgumentReference(typeof(IntPtr)));
            constructor.ConstructorBuilder.SetImplementationFlags(MethodImplAttributes.Runtime
                                                                  | MethodImplAttributes.Managed);
        }

        private void BuildInvokeMethod(AbstractTypeEmitter @delegate)
        {
            var paramTypes = GetParamTypes(@delegate);
            var invoke = @delegate.CreateMethod("Invoke",
                MethodAttributes.Public |
                MethodAttributes.HideBySig |
                MethodAttributes.NewSlot |
                MethodAttributes.Virtual,
                @delegate.GetClosedParameterType(method.MethodOnTarget.ReturnType),
                paramTypes);
            invoke.MethodBuilder.SetImplementationFlags(MethodImplAttributes.Runtime | MethodImplAttributes.Managed);
        }

        private AbstractTypeEmitter GetEmitter(ClassEmitter @class, INamingScope namingScope)
        {
            var methodInfo = method.MethodOnTarget;
            var suggestedName = string.Format("Castle.Proxies.Delegates.{0}_{1}",
                methodInfo.DeclaringType.Name,
                method.Method.Name);
            var uniqueName = namingScope.ParentScope.GetUniqueName(suggestedName);

            var @delegate = new ClassEmitter(@class.ModuleScope,
                uniqueName,
                typeof(MulticastDelegate),
                Type.EmptyTypes,
                DelegateFlags);
            @delegate.CopyGenericParametersFromMethod(method.Method);
            return @delegate;
        }

        private Type[] GetParamTypes(AbstractTypeEmitter @delegate)
        {
            var parameters = method.MethodOnTarget.GetParameters();
            if (@delegate.TypeBuilder.IsGenericType)
            {
                var types = new Type[parameters.Length];

                for (var i = 0; i < parameters.Length; i++)
                    types[i] = @delegate.GetClosedParameterType(parameters[i].ParameterType);
                return types;
            }
            var paramTypes = new Type[parameters.Length + 1];
            paramTypes[0] = targetType;
            for (var i = 0; i < parameters.Length; i++)
                paramTypes[i + 1] = @delegate.GetClosedParameterType(parameters[i].ParameterType);
            return paramTypes;
        }
    }
}